Method for manufacturing casting using lost wax process

TECHNICAL FIELD

The present invention relates to a method for manufacturing a casting based on precision casting using a lost wax process. More specifically, the present invention relates to a method for manufacturing a casting by fabricating a wax pattern with the use of a wax pattern forming die fabricated by stereolithography or a three-dimensional printer.

BACKGROUND ART

There is disclosed a method for forming a wax pattern having a hollow structure by using a die including an upper die and a lower die (see, e.g., Patent Document 1). According to this method for forming a wax pattern having a hollow structure, a desired hollow structure is formed in the wax pattern before the wax pattern is taken out of the die. Further, a hollow structure forming member is arranged at a position corresponding to the hollow structure of the wax pattern of the die, and this hollow structure forming member is made of a wax and then removed from the wax pattern. Furthermore, the hollow structure forming member has solubility, and this hollow structure forming member is dissolved and removed from the wax pattern after the wax is cured.

According to the method for forming a wax pattern having a hollow structure configured as described above, since the desired hollow structure is formed in the wax pattern when the wax pattern is removed from the die, productivity of casting manufacture in a lost wax process can be considerably improved. Moreover, when a member that is integrated with a casting is previously arranged at a position corresponding to the hollow structure of the wax pattern of the die in place of forming the hollow structure in the wax pattern, a material different from a casting material such as ceramics can be integrated with the casting.

On the other hand, there is disclosed a method for manufacturing a precision casting mold by which a surface of an evaporative pattern made of a photocurable resin and formed into substantially the same shape as a casting is coated with a refractory to form a precursor of a mold, and an oxygen containing gas is blown into the precursor at temperatures equal to or more than a decomposition temperature of the photocurable resin to combust and remove the evaporative pattern (see, e.g., Patent Document 2). According to this method for manufacturing a precision casting mold, stereolithography can be used as a method for fabricating an evaporative pattern. This stereolithography is implemented by inputting three-dimensional shape data of a casting to a computer, and irradiating a predetermined position of a photocurable resin liquid with light (a laser beam, an ultraviolet ray, or the like) based on this value to cure the resin. Additionally, a cured part is moved in a height direction, the uncured resin liquid is irradiated with the light in the similar manner to sequentially cure the resin liquid in the height direction, thereby fabricating a resin pattern. When the stereolithography is used, since a pattern is directly fabricated from the three-dimensional shape data, the pattern having a complicated shape or a small wall thickness can be highly precisely and easily fabricated, and production efficiency of the mold can be also improved.

According to the thus configured method for manufacturing a precision casting mold, since sufficient oxygen can be supplied at the time of combusting a resin, ambient oxygen concentration can be prevented from lowering with combustion of the resin. Consequently, since combustion of the resin is promoted and the greater part of the resin is combusted and removed in a short time without stopping, a stress load added to the mold by thermal expansion of the resin is reduced, and destruction of the mold can be avoided. Further, when the greater part of the resin is removed, an influence of the thermal expansion of the resin on the mold can be ignored, and hence then a residue (soot) in the mold can be completely combusted and removed over sufficient time.

PRIOR ART REFERENCES

Patent Documents

Patent Document 1: Japanese Unexamined Patent Application Publication No. Hei 9-122826 (claims 1 to 3, paragraphs [0014], [0015], and [0068])

Patent Document 2: Japanese Unexamined Patent Application Publication No. 2000-254759 (claim 1, paragraphs [0012], [0025], and [0026])

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

However, since the conventional method for forming a wax pattern having a hollow structure disclosed in Patent Document 1 requires a large amount of costs for fabrication of a die for forming a wax pattern and also requires a relatively large amount of costs for changing a shape of the die, in case of manufacturing a prototype on a preliminary step of manufacturing mass-produced items, relatively many man-hours are required at the time of changing a shape of a cavity in the die, and an inconvenience, i.e., a large amount of costs occurs when the shape of the cavity is changed frequently. Further, according to the conventional method for manufacturing a precision casting mold shown in Patent Document 2, although an evaporative pattern is fabricated by using the stereolithography, since this evaporative pattern is made of a photocurable resin which is a material different from the wax, there is a problem that special facilities or the like are required to vanish the evaporative pattern made of the photocurable resin. Furthermore, according to the conventional method for manufacturing a precision casting mold disclosed in Patent Document 2, in case of manufacturing a prototype on a preliminary step of manufacturing mass-produced items, a mold is fabricated by using an evaporative pattern, and a casting which is the prototype is fabricated with the use of this mold but, to examine cutting conditions or a change in shape of this casting, a plurality of castings are required depending on situations, and there is a problem that a plurality of evaporative patterns must be successively fabricated by the stereolithography which relatively takes time.

It is a first object of the present invention to provide a method for manufacturing a casting using a lost wax process, which enables changing a shape of a wax pattern forming die with a relatively few man-hours even if the shape of the wax pattern forming die is changed frequently in case of, e.g., manufacturing a prototype on a preliminary step of manufacturing mass-produced items. It is a second object of the present invention to provide a method for manufacturing a casting using a lost wax process, which enables fabricating a wax pattern with the use of a regular wax and eliminates the need for special facilities and the like to vanish the wax pattern. It is a third object of the present invention to provide a method for manufacturing a casting using a lost wax processing, which enables fabricating a plurality of wax patterns in a relatively short time. It is a fourth object of the present invention to provide a method for manufacturing a casting using a lost wax process, which enables easily forming a concave portion into a free shape in which a flow path through which a cooling medium to cool a wax pattern flows or a heatsink is inserted at the time of fabricating the wax pattern. It is a fifth object of the present invention to provide a method for manufacturing a casting using a lost wax process, which enables rapidly cooling a wax pattern by allowing a cooing medium to flow through the flow path or inserting a heatsink into the concave portion, and enables precisely transferring a shape of a cavity in a wax pattern forming die to the wax pattern.

Means for Solving the Problems

A first aspect of the present invention is, as shown in <figref idref="DRAWINGS">FIG. 1(<i>a</i>)</figref> to <figref idref="DRAWINGS">FIG. 4(<i>f</i>)</figref>, a method for manufacturing a casting using a lost wax process comprising steps of: fabricating a wax pattern forming die <b>13</b> to form a wax pattern <b>12</b>; pouring a molten wax into a cavity <b>14</b><i>a </i>in the wax pattern forming die <b>13</b> to fabricate the wax pattern <b>12</b>; bonding the wax pattern <b>12</b> to a casting sprue pattern <b>28</b> made of the wax and fabricated separately from the wax pattern <b>12</b> to fabricate an integrated pattern <b>29</b>; coating a surface of the integrated pattern <b>29</b> with ceramics, sintering the pattern, and then melting and effusing the integrated pattern <b>29</b> to fabricate a mold <b>32</b> to mold a casting with a casting sprue <b>31</b>; pouring a molten metal into the mold <b>32</b>, curing the metal, and then crushing the mold <b>32</b> to take out the casting with a casting sprue <b>31</b>; cutting off a casting sprue <b>33</b> from the casting with a casting sprue <b>31</b> to fabricate the casting <b>11</b>, wherein the wax pattern forming die <b>13</b> is a resin forming die that is sterically formed by using stereolithography or a three-dimensional printer and has a heat resistance temperature higher than a temperature of the molten wax.

A second aspect of the present invention is the invention based on the first aspect and, as shown in <figref idref="DRAWINGS">FIG. 1(<i>a</i>)</figref> to <figref idref="DRAWINGS">FIG. 4(<i>f</i>)</figref>, is characterized in that further the plurality of wax patterns <b>12</b> are fabricated at the time of fabrication of the wax pattern <b>12</b>, and the plurality of wax patterns <b>12</b> are bonded to the single casting sprue pattern <b>28</b> in a tree shape at the time of fabrication of the integrated pattern <b>29</b> to fabricate the integrated pattern <b>29</b>.

A third aspect of the present invention is the invention based on the first aspect and, as shown in <figref idref="DRAWINGS">FIG. 5</figref>, is characterized in that further flow paths <b>51</b> and <b>52</b> are formed in the wax pattern forming die <b>53</b> in proximity to an inner surface of a cavity <b>57</b> having a shape corresponding to the wax pattern at the time of fabrication of the wax pattern forming die <b>53</b> so that a cooling medium is allowed to flow through the flow paths <b>51</b> and <b>52</b>.

A fourth aspect of the present invention is the invention based on the third aspect and, as shown in <figref idref="DRAWINGS">FIG. 5</figref>, is characterized in that further the cooling medium is pressurized air from a water tank air pump <b>61</b>, and the wax is poured into the cavity <b>57</b> and cooled down while keeping the pressurized air flowing in from an inlet <b>51</b><i>a </i>of the flow path <b>51</b> and being discharged from an outlet <b>52</b><i>b </i>of the flow path <b>52</b>.

A fifth aspect of the present invention is the invention based on the first aspect and, as shown in <figref idref="DRAWINGS">FIG. 6</figref>, is characterized in that further concave portions <b>81</b> and <b>82</b> extending from an outer surface of the wax pattern forming die <b>83</b> to the inside of the wax pattern forming die <b>83</b> close to an inner surface of a cavity <b>57</b> having a shape corresponding to the wax pattern are formed at the time of fabrication of the wax pattern forming die <b>83</b> so that insertion of heatsinks <b>91</b> and <b>92</b> into the concave portions <b>81</b> and <b>82</b> is enabled.

Effects of the Invention

In the method for manufacturing a casting using a lost wax process according to the first aspect of the present invention, since the wax pattern forming die is the resin forming die that is sterically formed by using the stereolithography or the three-dimensional printer and has a heat resistance temperature higher than a temperature of the molten wax, even if a shape of the wax pattern forming die is frequently changed in case of, e.g., manufacturing a prototype on a preliminary step of manufacturing mass-produced items, the shape of the wax pattern forming die can be changed with a relatively few man-hours. That is, since fabrication of a die for forming the wax pattern requires a large amount of costs and changing the shape of this die requires a relatively large amount of costs, as compared with the conventional method for forming a wax pattern having a hollow structure requiring a large amount of costs, even if the shape of the cavity in the die is frequently changed in the present invention, changing the three-dimensional shape data used in the stereolithography or the three-dimensional printer can suffice, and hence the shape of the wax pattern forming die can be changed with a relatively few man-hours. Furthermore, since the evaporative pattern fabricated with the use of the stereolithography is made of the photocurable resin that is a different material from the wax, the wax pattern can be fabricated from the regular wax in the present invention as compared with the conventional method for manufacturing a precision casting mold that has the problem requiring special facilities and others to vanish the evaporative pattern made of the photocurable resin, and hence special facilities and others to vanish the wax pattern are not required.

In the method for manufacturing a casting using a lost wax process according to the second aspect of the present invention, since the plurality of wax patterns are fabricated in wax pattern fabrication and the plurality of wax patterns are bonded to the single casting sprue pattern in the form of a tree at the time of fabrication of the integrated pattern to fabricate the integrated pattern, the plurality of wax patterns can be fabricated in a relatively short time. That is, as compared with the conventional method for manufacturing a precision casting forming die by which a plurality of evaporative patterns must be sequentially fabricated based on the stereolithography which relatively takes time, a plurality of wax patterns can be fabricated based on injection molding or the like in a relatively short time in the present invention.

In the method for manufacturing a casting using a lost wax process according to the third aspect of the present invention, since the flow paths are formed in the wax pattern forming die in proximity to the inner surface of the cavity having the shape corresponding to the wax pattern, at the time of fabrication of the wax pattern using the wax pattern forming die, the cooling medium draws heat of the wax in the cavity by allowing the cooling medium to flow through the flow paths, and hence the wax pattern can be rapidly cooled. Consequently, the shape of the cavity in the wax pattern forming die can be precisely transferred to the wax pattern. Further, since the wax pattern forming die is formed by using the stereolithography or the three-dimensional printer, the flow path through which the cooling medium flows can be easily formed into a free shape.

In the method for manufacturing a casting using a lost wax process according to the fourth aspect of the present invention, the cooling medium is the pressurized air from the water tank pump, the wax is poured into the cavity and cooled down while keeping this pressured air flowing in from the inlet of the flow path and being discharged to the outlet of the flow path, and hence the air discharged from the outlet of the flow path can be emitted into the atmosphere as it is. Consequently, as compared with a case where a liquid which requires a drainage treatment is used as the cooling medium, the drainage treatment can be eliminated, and hence the cooling medium can be relatively easily handled.

In the method for manufacturing a casting using a lost wax process according to the fifth aspect of the present invention, since the concave portions which extend from the outer surface of the wax pattern forming die to the inside of the same close to the inner surface of the cavity having the shape corresponding to the wax pattern is formed in the wax pattern forming die, the heatsinks draw heat of the wax in the cavity by inserting the heatsinks into these concave portions, and the wax pattern can be rapidly cooled. Consequently, the shape of the cavity in the wax pattern forming die can be precisely transferred to the wax pattern. Further, since the wax pattern forming die is formed by using the stereolithography or the three-dimensional printer, the concave portions into which the heatsinks are inserted can be easily formed into a relatively free shape.

BRIEF DESCRIPTION OF THE DRAWINGS

<figref idref="DRAWINGS">FIGS. 1(<i>a</i>)-1(<i>e</i>)</figref> is a process chart showing a procedure of fabricating a wax pattern by using a wax pattern forming die according to a first embodiment of the present invention;

<figref idref="DRAWINGS">FIGS. 2(<i>a</i>)-2(<i>c</i>)</figref> is schematic cross-sectional views showing an optical lamination forming method for manufacturing a movable side resin die of the wax pattern forming die, where <figref idref="DRAWINGS">FIG. 2(<i>a</i>)</figref> shows a state where a first cured thin layer having a predetermined shape is formed, <figref idref="DRAWINGS">FIG. 2(<i>b</i>)</figref> shows a state where a table is slightly moved downward to form a second cured thin layer, and <figref idref="DRAWINGS">FIG. 2(<i>c</i>)</figref> shows a state where the movable side resin die which is an optically formed product having a predetermined three-dimensional shape is formed;

<figref idref="DRAWINGS">FIGS. 3(<i>a</i>)-3(<i>c</i>)</figref> is schematic cross-sectional views showing the optical lamination forming method for manufacturing a fixed side resin die of the wax pattern forming die, where <figref idref="DRAWINGS">FIG. 3(<i>a</i>)</figref> shows a state where a first cured thin layer having a predetermined shape is formed, <figref idref="DRAWINGS">FIG. 3(<i>b</i>)</figref> shows a state where the table is slightly moved downward to form a second cured thin layer, and <figref idref="DRAWINGS">FIG. 3(<i>c</i>)</figref> shows a state where a fixed side resin die which is an optically formed product having a predetermined three-dimensional shape is formed;

<figref idref="DRAWINGS">FIGS. 4(<i>a</i>)-4(<i>f</i>)</figref> is a process chart showing a procedure of manufacturing a casting based on a lost wax process using the wax pattern;

<figref idref="DRAWINGS">FIG. 5</figref> is a cross-sectional block diagram of a wax pattern forming die according to a second embodiment of the present invention; and

<figref idref="DRAWINGS">FIG. 6</figref> is a cross-sectional block diagram of a wax pattern forming die according to a third embodiment of the present invention.

EMBODIMENTS TO CARRY OUR THE INVENTION

A mode for carrying out the present invention will now be described with reference to the drawings.

&lt;First Embodiment&gt;

As shown in <figref idref="DRAWINGS">FIG. 1(<i>a</i>)</figref> to <figref idref="DRAWINGS">FIG. 3(<i>c</i>)</figref>, a method for manufacturing a casting <b>11</b> using a lost wax process includes a step of fabricating a wax pattern forming die <b>13</b> to form a wax pattern <b>12</b>, and a step of pouring a molten wax into a cavity <b>14</b><i>a </i>of this wax pattern forming die <b>13</b> to fabricate the wax pattern <b>12</b>. The wax pattern forming die <b>13</b> is a molding die made of a resin which is sterically formed by using stereolithography or a three-dimensional printer and has a heat resistance temperature higher than a temperature of the molten wax. Furthermore, the wax pattern forming die <b>13</b> has a movable side resin die <b>14</b> in which a cavity <b>14</b><i>a </i>to fabricate the cylindrical wax pattern <b>12</b> is formed, and a fixed side resin die <b>16</b> in which a runner <b>16</b><i>a </i>through which the molten wax is poured into this cavity <b>14</b><i>a </i>is formed. The movable side resin die <b>14</b> is fitted in a non-illustrated movable base, the fixed side resin die <b>16</b> is fitted in a non-illustrated fixed base, and the movable side resin die <b>14</b> is configured to be movable in a direction to get closer and adhere tightly to the fixed side resin die <b>16</b> and a direction to recede and get away from the fixed side resin die <b>16</b> (<figref idref="DRAWINGS">FIGS. 1(<i>a</i>)-1(<i>e</i>)</figref>). Moreover, in this embodiment, the movable side resin die <b>14</b> and the fixed side resin die <b>16</b> are sterically formed by using the stereolithography (<figref idref="DRAWINGS">FIG. 2</figref> and <figref idref="DRAWINGS">FIGS. 3(<i>a</i>)-3(<i>c</i>)</figref>). Specifically, the movable side resin die <b>14</b> and the fixed side resin die <b>16</b> as optically formed products are fabricated by optical stereolithography as typified by an optical lamination forming method.

<figref idref="DRAWINGS">FIGS. 2(<i>a</i>) to (<i>c</i>)</figref> show steps of forming the movable side resin die <b>14</b> by the optical lamination forming method. Three-dimensional data of a formed product corresponding to the movable side resin die <b>14</b> is acquired in advance, this data is cut in round slices at equal intervals in computations and stored as slice data. First, as shown in <figref idref="DRAWINGS">FIG. 2(<i>a</i>)</figref>, a table <b>24</b> movable in a perpendicular direction is arranged in a container <b>22</b> accommodating a liquid photocurable composition <b>21</b> so that an upper face of the table <b>24</b> is placed at a position that is slightly below a liquid level <b>23</b> of the liquid photocurable composition <b>21</b>. The liquid photocurable composition <b>21</b> contains a radial polymerizable compound such as a (meta)acrylic monomer, a polymerizable monomer containing a cationically polymerizable compound such as an epoxy compound, a photopolymerization initiator, and others. After arranging the table <b>24</b>, a thin layer of the liquid photocurable composition <b>21</b> on this table <b>24</b> is scanned with an ultraviolet laser beam <b>27</b> from an ultraviolet laser apparatus <b>26</b> in a predetermined pattern based on the stored data to form a first cured thin layer <b>14</b><i>b </i>having a predetermined shape. Then, as shown in <figref idref="DRAWINGS">FIG. 2(<i>b</i>)</figref>, the thin layer of the liquid photocurable composition <b>21</b> is formed on the first curable thin layer <b>14</b><i>b </i>by slightly moving a position of the table <b>24</b> downward, and then this thin layer is scanned with the ultraviolet laser beam <b>27</b> in a predetermined pattern based on the stored data, thereby forming a second cured thin layer <b>14</b><i>c </i>having a predetermined shape. Thereafter, the same operation is repeated, and the movable side resin die <b>14</b> which is an optically formed product having a predetermined stereoscopic shape as an aggregation of the plurality of cured thin layers <b>14</b><i>b</i>, <b>14</b><i>c</i>, . . . , <b>14</b><i>x </i>is finally provided as shown in <figref idref="DRAWINGS">FIG. 2(<i>c</i>)</figref>.

<figref idref="DRAWINGS">FIGS. 3(<i>a</i>) to (<i>c</i>)</figref> show steps of forming the fixed side resin die <b>16</b> by the optical lamination forming method, and this die is fabricated by the same method as the movable side resin die <b>14</b>. Further, the fixed side resin die <b>16</b> which is the optically formed product having a predetermined stereoscopic shape which is an aggregation of a plurality of cured thin layers <b>16</b><i>b</i>, <b>16</b><i>c</i>, . . . , <b>16</b><i>x </i>is provided. To fabricate a wax pattern using the wax pattern forming die <b>13</b>, first, the movable side resin die <b>14</b> is fitted into a movable base, the fixed side resin die <b>16</b> is fitted into a fixed base, the movable side resin die <b>14</b> is adhered tightly to the fixed side resin die <b>16</b> so that the cavity <b>14</b><i>a </i>of the movable side resin die <b>14</b> and the runner <b>16</b><i>a </i>of the fixed side resin die <b>16</b> are continuously connected and clamped (<figref idref="DRAWINGS">FIG. 1(<i>a</i>)</figref>), and the molten wax is poured into the runner <b>16</b><i>a </i>and the cavity <b>14</b><i>a </i>in this state (<figref idref="DRAWINGS">FIG. 1(<i>b</i>)</figref>). Then, after the poured wax is cooled and cured, the movable side resin die <b>14</b> is receded and disconnected from the fixed side resin die <b>16</b> (<figref idref="DRAWINGS">FIG. 1(<i>c</i>)</figref>). Furthermore, after a wax pattern with a wax pattern sprue <b>17</b> is taken out of the movable side resin die <b>14</b>, a wax pattern sprue <b>18</b> is cut off from the wax pattern with the wax pattern sprue <b>17</b> to fabricate the wax pattern <b>12</b> (<figref idref="DRAWINGS">FIG. 1(<i>d</i>)</figref>). It is to be noted that the movable side resin die and the fixed side resin die are fabricated by the optical lamination forming method in this embodiment, but the movable side resin die and the fixed side resin die may be fabricated by a three-dimensional printer. Specifically, the movable side resin die and the fixed side resin die may be fabricated by a three-dimensional printer adopting an inkjet ultraviolet curing system using an acrylic photocurable resin, a three-dimensional printer adopting a thermal dissolution laminating system using an ABS resin (an acrylonitrile-butadiene-styrene copolymer synthetic resin), or a three-dimensional printer adopting a powder fixing system using powder.

Moreover, the wax pattern forming die <b>13</b> according to the present invention does not contain materials intended to make strength or heat resistance of a carbon material, a metal material, a ceramic material, or the like closer to that of a conventional die in terms of a material, i.e., materials other than a resin. Thus, a heat resistance temperature of the wax pattern forming die <b>13</b> according to the present invention is dependent on a material of a starting material resin, but it is in the range of 70 to 100° C. Additionally, as the wax poured into the cavity <b>14</b><i>a </i>of the wax pattern forming die <b>13</b>, paraffin, a filler wax provided by dispersing particles of polymethylmethacrylate, particles of agarose, or particles of fibrous glass or calcium carbonate in the paraffin, or the like is used, and a melting temperature at the time of pouring this wax into the cavity <b>14</b><i>a </i>is in the range of 50 to 80° C. (usually, approximately 60° C.). In this specification, the “heat resistance temperature of the wax pattern forming die <b>13</b>” means a maximum temperature at which the material constituting the wax pattern forming die <b>13</b> maintains the same configuration as that at a room temperature (25° C.) without causing alteration such as decomposition or dissolution.

On the other hand, as shown in <figref idref="DRAWINGS">FIGS. 4(<i>a</i>)-4(<i>f</i>)</figref>, the method for manufacturing the casting <b>11</b> using the lost wax process further includes a step of bonding the wax pattern <b>12</b> to a casting sprue pattern <b>28</b> made of the wax and fabricated aside from the wax pattern <b>12</b> to fabricate an integrated pattern <b>29</b> (<figref idref="DRAWINGS">FIG. 4(<i>a</i>)</figref>), a step of coating a surface of this integrated pattern <b>29</b> with ceramics, performing sintering, and then melting and effusing the integrated pattern <b>29</b> to fabricate a mold <b>32</b> to cast a casting with a casting sprue <b>31</b> (<figref idref="DRAWINGS">FIG. 4(<i>b</i>)</figref> and <figref idref="DRAWINGS">FIG. 4(<i>c</i>)</figref>), a step of pouring a molten metal into this mold <b>32</b>, curing the molten metal, and then crushing the mold <b>32</b> to take out a casting with a casting sprue <b>31</b> (<figref idref="DRAWINGS">FIG. 4(<i>d</i>)</figref> and <figref idref="DRAWINGS">FIG. 4(<i>e</i>)</figref>), and a step of cutting off a casting sprue <b>33</b> from the casting with the casting sprue <b>31</b> to fabricate the casting <b>11</b> (<figref idref="DRAWINGS">FIG. 4(<i>f</i>)</figref>). In this embodiment, the casting sprue pattern <b>28</b> is formed with the use of the die, and a material of the molten wax poured into this casting sprue pattern <b>28</b> is the same as that of the molten wax poured into the wax pattern forming die <b>13</b>. Additionally, in this embodiment, the plurality of wax patterns <b>12</b> are fabricated, the single casting sprue pattern <b>28</b> is fabricated, and the plurality of wax patterns <b>12</b> are bonded to this single casting sprue pattern <b>28</b> in the tree shape to fabricate the integrated pattern <b>29</b>. Further, as the ceramics to be coated on the surface of the integrated wax <b>29</b>, there is zirconium silicate, aluminum, silica, or the like, and sintering is carried out at a sintering temperature of the coating ceramics in the range of 1000 to 1100° C. Further, as the metal that is poured into the mold <b>32</b>, there are many kinds of metals which can be treated in a precision casting method, e.g., an iron-based alloy, a copper alloy, an aluminum alloy, a titanium alloy, and others.

It is to be noted that, in this embodiment, the plurality of wax patterns are fabricated in the wax pattern fabrication, the plurality of wax patterns are bonded to the casting sprue pattern in the tree shape in the integrated pattern fabrication to fabricate the integral pattern, but the single wax pattern may be fabricated in the wax pattern fabrication, and the single wax pattern may be bonded to the casting sprue pattern in the integrated pattern fabrication to fabricate the integrated pattern. Furthermore, in this embodiment, the casting sprue pattern is fabricated by using the casting sprue pattern forming die made of the metal, but the casting sprue pattern forming die may be fabricated by using the optical lamination forming method or the three-dimensional printer, and the casting sprue pattern may be fabricated by using this casting sprue pattern forming die.

In the thus configured method for manufacturing the casting <b>11</b> using the lost wax process, since the wax pattern forming die <b>13</b> is a resin forming die that is sterically formed by using the stereolithography or the three-dimensional printer and has the heat resistance temperature higher than a temperature of the molten wax, the shape of the wax pattern forming die <b>13</b> can be changed with a relatively few man-hours even if the shape of the wax pattern forming die <b>13</b> is frequently changed in case of manufacturing, e.g., a prototype on a preliminary step of manufacturing mass-produced items. That is, in the conventional method for forming a wax pattern having a hollow structure, since fabrication of a die for forming a wax pattern requires a large amount of costs and changing a shape of this die requires a relatively large amount of costs, enormous costs are required when a shape of a cavity in the die is frequently changed, whereas, in the wax pattern forming die <b>13</b> according to this embodiment, changing the three-dimensional shape data used in the stereolithography or the three-dimensional printer can suffice even if the shape of this wax pattern forming die <b>13</b> is frequently changed, and hence the shape of the wax pattern forming die <b>13</b> can be changed with a relatively few man-hours. Moreover, in the conventional method for manufacturing a precision casting mold, since an evaporative pattern fabricated by using the stereolithography is made of a photocurable resin which is a material different from the wax, there is a problem that special facilities and the like are required to vanish this evaporative pattern made of the photocurable resin, whereas, in this embodiment, the wax pattern <b>12</b> can be fabricated with the use of the regular wax, and hence no special facilities and others are required to vanish the wax pattern <b>12</b>. Additionally, in this embodiment, since the plurality of wax patterns <b>12</b> are bonded to the single casting sprue pattern <b>28</b> in the tree shape to fabricate the integrated pattern <b>29</b>, the plurality of wax patterns <b>12</b> can be fabricated in a relatively short time. That is, the plurality of evaporative patterns must be sequentially fabricated by the stereolithography which relatively requires time in the conventional method for manufacturing a precision casting mold, whereas the plurality of wax patterns <b>12</b> can be fabricated in a relatively short time by injection molding or the like in this embodiment.

&lt;Second Embodiment&gt;

<figref idref="DRAWINGS">FIG. 5</figref> shows a second embodiment according to the present invention. In this embodiment, at the time of fabricating a wax pattern forming die <b>53</b>, first and second flow paths <b>51</b> and <b>52</b> are formed in the wax pattern forming die <b>53</b> in proximity to an inner surface of a cavity <b>57</b> having a shape corresponding to a wax pattern respectively so that a cooling medium can flow through these first and second flow paths <b>51</b> and <b>52</b>. Specifically, in this embodiment, the wax pattern is formed into a bowl-like shape. Further, the wax pattern forming die <b>53</b> has a fixed side resin die <b>56</b> in which an outer surface of the cavity <b>57</b> for fabrication of the bowl-like wax pattern is formed and a runner <b>58</b> for pouring a molten wax into the cavity <b>57</b> is also formed, and a movable side resin die <b>54</b> in which an inner surface of the cavity <b>57</b> is formed. Furthermore, assuming that a volume of the cavity <b>57</b> is 1, a volume of the wax pattern forming die <b>53</b> is 40 to 200. The first flow path <b>51</b> through which the cooling medium flows is formed in the fixed side resin die <b>56</b> at a position close to the inner surface of the bowl-like cavity <b>57</b>, and the second flow path <b>52</b> through which the cooling medium flows is formed in the movable side resin die <b>54</b> at a position close to the inner surface of the bowl-like cavity <b>57</b>. Here, “close to the inner surface of the cavity <b>57</b>” means being placed in the range of 2 to 15 mm from the curved inner surface of the bowl-like cavity <b>57</b> on the outer side or the curved inner surface of the bowl-like cavity <b>57</b> on the inner side. In this embodiment, air is pressurized to flow as the cooling medium through the first and second flow paths. It is to be noted that a liquid such as a gas or water other than the air may be pressurized to flow through the first flow path and the second flow path. However, in this case, a drainage treatment is required. When the wax pattern forming die <b>53</b> is manufactured by the stereolithography or three-dimensional printer, each of the first and second flow paths <b>51</b> and <b>52</b> can be formed with a diameter falling within the range of 1 to 6 mm that enables passage of a pressurized gas such as pressurized air, or preferably a diameter of 2 mm or less, or a diameter falling within the range of 4 to 6 mm that enables passage of a pressured liquid such as pressurized water even if the cavity <b>57</b> has a complicated shape. Moreover, the first and second flow paths <b>51</b> and <b>52</b> can be formed at an interval of 1 to 5 mm in proximity to the cavity <b>57</b>.

On the other hand, in mold clamping of the wax pattern forming die <b>53</b>, an outlet <b>51</b><i>b </i>of the first flow path <b>51</b> and an inlet <b>52</b><i>a </i>of the second flow path <b>52</b> face to each other to form a connection port <b>59</b>. Consequently, the first low path <b>51</b> and the second flow path <b>52</b> form one continuous flow path. In this embodiment, the cooling medium is the pressurized air from a water tank air pump <b>61</b>, the wax is poured into the cavity <b>57</b> and cooled down while keeping the pressurized air flowing in from an inlet <b>51</b><i>a </i>of the first flow path <b>51</b> and flowing out from an outlet <b>52</b><i>b </i>of the second flow path <b>52</b> through the connection port <b>59</b>. Specifically, an air pipe <b>62</b> of the single small water tank air pump <b>61</b> that operates with a power supply of 100 V is connected to the inlet <b>51</b><i>a </i>of the first flow path <b>51</b>. This water tank air pump <b>61</b> is a pump that brings about aeration in a water tank for aquarium fish such as goldfish or tropical fish. Further, a known wax injection molding apparatus (not shown) is connected to the runner <b>58</b>, and this injection molding apparatus is loaded with the wax. Other structures are the same as those in the first embodiment.

In the thus configured method for manufacturing a casting using the lost wax process, since the first and second flow paths <b>51</b> and <b>52</b> are formed in the wax pattern forming die <b>53</b> in proximity to the inner surface of the cavity <b>57</b> having the shape corresponding to the wax pattern, the pressurized air draws heat from the wax in the cavity <b>57</b> by allowing the pressurized air to flow through the first and second flow paths <b>51</b> and <b>52</b> at the time of fabrication of the wax pattern using the wax pattern forming die <b>53</b>, thereby rapidly cooling the wax pattern. Consequently, the shape of the cavity <b>57</b> in the wax pattern forming die <b>53</b> can be precisely transferred to the wax pattern. Furthermore, since the wax pattern forming die <b>53</b> is formed by using the stereolithography or the three-dimensional printer, the first and second flow paths <b>51</b> and <b>52</b> through which the pressurized air flows can be easily formed into free shapes. Moreover, the wax is poured into the cavity <b>57</b> and cooled down while keeping the pressurized air flowing in from the inlet <b>51</b><i>a </i>of the first flow path <b>51</b> and being discharged from the outlet <b>52</b><i>b </i>of the second flow path <b>52</b> through the connection port <b>59</b> by using the water tank air pump <b>61</b>, and hence the pressured air discharged from the outlet <b>52</b><i>b </i>of the second flow path <b>52</b> can be directly emitted into the atmosphere. Consequently, as compared with a case where a liquid requiring a drainage treatment is used as the cooling medium, since this embodiment does not require the drainage treatment, the pressurized air as the cooling medium can be relatively easily treated. Other operations are substantially the same as the operations in the first embodiment, and hence a tautological description will be omitted.

&lt;Third Embodiment&gt;

<figref idref="DRAWINGS">FIG. 6</figref> shows a third embodiment according to the present invention. In <figref idref="DRAWINGS">FIG. 6</figref>, like reference numerals denote parts equal to those in <figref idref="DRAWINGS">FIG. 5</figref>. In this embodiment, first and second concave portions <b>81</b> and <b>82</b> are formed respectively at the time of fabrication of a wax pattern forming die <b>83</b>, the first and second concave portions <b>81</b> and <b>82</b> extending from an outer surface of the wax pattern forming die <b>83</b> to the inside of the wax pattern forming die <b>83</b> which is close to an inner surface of a cavity <b>57</b> having a shape corresponding to a wax pattern. The first and second concave portions <b>81</b> and <b>82</b> are configured so that first and second heatsinks <b>91</b> and <b>92</b> can be inserted into these portions respectively. Specifically, in this embodiment, the wax pattern is formed into a bowl-like shape like the second embodiment. Furthermore, the first concave portion <b>81</b> into which the first heatsink <b>91</b> is inserted is formed at a portion in a fixed side resin die <b>86</b> of the wax pattern forming die <b>83</b> close to the inner surface of the cavity <b>57</b>, and the second concave portion <b>82</b> into which the second heatsink <b>92</b> is inserted is formed at a portion in a movable side resin die <b>84</b> close to the inner surface of the cavity <b>57</b>. As a material of the first and second heatsinks <b>91</b> and <b>92</b>, there is a metal having high thermal conductivity such as aluminum, an aluminum alloy, copper, or a copper alloy, and ceramics having high thermal conductivity such as an aluminum nitride may be used. Moreover, it is preferable to form each of the first and second concave portions <b>81</b> and <b>82</b> into a cylindrical shape, a square columnar shape, or any other columnar shape, and preferable to form each of the first and second heatsinks <b>91</b> and <b>92</b> into a cylindrical shape, a square columnar shape, or any other columnar shape corresponding to the first and second concave portions. Additionally, in a state where the first heatsink <b>91</b> is inserted into the first concave portion <b>81</b> and the second heatsink <b>92</b> is inserted into the second concave portion <b>82</b>, the molten wax is poured into the cavity <b>57</b> and cooled down. Other structures are the same as those in the second embodiment.

In the thus configured method for manufacturing a casting using the lost wax process, since the first and second concave portions <b>81</b> and <b>82</b> extending from the outer surface of the wax pattern forming die <b>83</b> to the inside of the wax pattern forming die <b>83</b> close to the inner surface of the cavity <b>57</b> corresponding to the wax pattern are formed respectively, the first and second heatsinks <b>91</b> and <b>92</b> draw heat from the wax in the cavity <b>57</b> by inserting the first and second heatsinks <b>91</b> and <b>92</b> into the first and second concave portions <b>81</b> and <b>82</b> respectively, thereby rapidly cooling the wax pattern. Consequently, the shape of the cavity <b>57</b> in the wax pattern forming die <b>83</b> can be precisely transferred to the wax pattern. Additionally, since the wax pattern forming die <b>83</b> is formed by using the stereolithography or the three-dimensional printer, each of the first and second concave portions <b>81</b> and <b>82</b> into which the first and second heatsinks <b>91</b> and <b>92</b> are inserted can be easily formed into a relatively free shape. Other operations are substantially the same as the operations in the second embodiment, and hence a tautological description will be omitted.

The method for manufacturing a casting using a lost wax process according to the present invention can be used for easily and cheaply manufacturing castings for trial production of toys, convenience goods, automobile components, or electrical components.